An impressive array of unique female genital tract proteins are being found whose occurrence coincides with specific events in the reproductive processes of mammals. Preliminary studies have shown that some of these are under direct hormonal control and that they exercise an influence on development of the embryo. The main objective of the research proposed here is to clarify the role of certain of these proteins, particularly the rabbit uterine protein, blastokinin, in reproduction. A second objective is to apply this information in developing methods of contraception that depend on limiting the production or availability of these proteins. The studies to be undertaken will utilize the rabbit as the main experimental animal. They will focus on questions of how specific uterine proteins relate to; the endometrial tissues that seem to produce them, the hormonal state of the mother, induction of new protein synthesis and/or ultrastructural changes in embryonic cells, sperm capacitation, luteolysis; and whether they are species specific and can be used as antigens in an immunological method for preventing or disrupting pregnancy. The methods to be used will be standard ones for molecular sieving, pressure dialysis, lypholization, and acrylamide gel electrophoresis to isolate and identify proteins, embryo culture, surgical and injection procedures and immunological techniques for determining specificity and influencing pregnancy.